1
Q
Essential components that mange various operations within a computer network
A
Network Services
2
Q
Used to uniquely identify a network interface card on a given network
A
MAC Address
3
Q
To avoid issues, duplicate MAC addresses should not exist on the network | enable port security on the switches
A
Having two or more devices responding to data requests from the same MAC address can cause significant network issues
4
Q
Listens to multicast messages on a network and keeps track of the MAC addresses being used
A
Logical Domain Manager
5
Q
Occurs when another computers on the same network has an identical IP to another workstataion or server on the same network
A
Duplicate IP Address/IP Address Conflict
6
Q
Static IP address issue
dhcp server issue
rogue dhcp server
A
start by checking whether the client is dynamically or statically assigned an IP address
7
Q
Network management protocol used on IP networks to automatically assign IP addresses and other communication parameters to devices connected to the network using a client-server architecture
A
Dynamic Host Configuration Protocol (DHCP)
8
Q
A DHCP server on a network which is not under the administrative control of network administrators
A
Rogue DHCP Server
9
Q
To prevent a rogue DHCP server from connecting to the network, configure DHCP snooping on the network
A
DHCP snooping, port security, intrusion detection
10
Q
Occurs when the DHCP server runs out of valid IPs to assign to the clients requesting access on the network | longer lease times can lead to DHCP scope exhaustion
A
DHCP Scope Exhaustion
11
Q
Another strategy to address DHCP scope exhaustion is to increase the size of the scope
A
The final thing you can do is decrease the number of devices that are using the DHCP server and in turn, the IP addresses from its scope - enable port security or network access control (NAC)
12
Q
Routing issues that you come across your network:
A
Multicast flooding - No specific host is associated with the multicast MAC address in the CAM table of the switch | configure the switch to block unknown multicast packets
Asymmetrical routing - Network packets leave via one path and return via a different path | in scenarios involving load balancing and protocols like HSRP, asymmetric routing asymmetric routing can occur
Missing routes - When a router cannot reach a destination because there is a missing route in the routing table | verify that the dynamic routing protocol is enabled and ensure that the two routers can communicate with each other
13
Q
Routing issues cause issues with dropped packets flows
A
14
Q
What is multicast networking?
A
Multicast sends traffic to multiple destination devices simultaneously using a single multicast address.
15
Q
How does multicast communication work?
A
Traffic is sent to one multicast IP/MAC address
The network distributes it to all members of the multicast group
16
Q
What is multicast flooding?
A
Multicast flooding occurs when multicast traffic is sent to all devices in a LAN or VLAN, even those that did not request it.
17
Q
Q: What causes multicast flooding?
A
No specific host is associated with the multicast MAC address
The multicast MAC is missing from the switch’s CAM table
18
Q
What does the switch do when multicast MAC information is missing?
A
It floods multicast traffic out all ports in the VLAN.
19
Q
Q: Why is multicast flooding a problem?
A
Creates unnecessary traffic
Wastes network resources
Can degrade network performance
20
Q
Q: How do you prevent multicast flooding?
A
Configure the switch to block unknown multicast packets
21
Q
Q: Do you need to know switch commands for the exam?
A
No. You only need to know that blocking unknown multicast traffic solves the problem.
22
Q
Exam Takeaway (High-Yield):
A
Multicast flooding = missing multicast MAC in CAM table
Solution = block unknown multicast traffic
23
Q
Q: What is multicast networking?
A
A: Multicast sends traffic to multiple destination devices simultaneously using a single multicast address.
24
Q
What is multicast networking?
A
Multicast sends one message to a single multicast address, which is then distributed to a group of destination hosts simultaneously.
Multicast = one-to-many communication.
25
What is multicast flooding?
Multicast flooding occurs when no specific host is associated with a multicast MAC address in the switch’s CAM table, causing multicast traffic to be flooded across the entire LAN or VLAN.
Multicast flooding wastes bandwidth and network resources.
26
Q: Why does multicast flooding happen on a switch?
Because the switch does not know where to forward multicast traffic, so it sends it everywhere.
Unknown multicast MAC = flooding behavior.
27
Q: How do you prevent multicast flooding?
Configure the switch to block unknown multicast packets.
You don’t need to know commands, just know that blocking unknown multicast traffic fixes the issue.
28
Q: What is asymmetrical routing?
Asymmetrical routing occurs when packets leave the network on one path and return on a different path.
Outbound path ≠ inbound path.
29
Q: Where does asymmetrical routing commonly occur?
Across different Layer 2 bridge interfaces
Across multiple routers or firewalls
In high-availability (HA) clusters
When using load balancing (e.g., HSRP)
HA and load-balanced environments are high risk.
30
Q: Why is asymmetrical routing a problem for security devices?
Stateful firewalls and deep packet inspection devices must see the entire packet flow; asymmetric routing prevents this.
Security devices are state-aware, not stateless.
31
Q: How do routers handle packet forwarding related to asymmetrical routing?
Routers attempt consistent forwarding in one direction only and do not control return traffic paths.
Routers prioritize fastest delivery, not symmetry.
32
Q: Why do firewall clusters cause asymmetrical routing?
All cluster nodes advertise paths to the same networks, so routers may choose different nodes for inbound and outbound traffic.
Exam Takeaway:
Multiple valid paths = packet flow split.
33
Q: What happens to traffic during asymmetrical routing in firewall clusters?
Traffic may be dropped because one or both firewalls don’t see the full session.
Dropped packets = intermittent connectivity issues.
34
Q: How do you fix asymmetrical routing issues?
Adjust firewall placement and routing so traffic flows through the same firewall in both directions.
Design matters more than configuration.
35
Q: Where should firewalls be placed to prevent asymmetrical routing?
Closer to the systems they protect, not only at the network edge.
Firewall placement is a network architecture decision.
36
Q: What are missing routes?
Missing routes occur when a router cannot reach a destination because the route is not in its routing table.
No route = no connectivity.
37
Q: What commonly causes missing routes?
Mistyped static routes
Incorrect routing commands
Dynamic routing protocols not converging
Exam Takeaway: Static routes are error-prone.
38
Q: How do you troubleshoot missing routes?
show ip route (router/switch)
route print (Windows)
Verify dynamic routing (OSPF/BGP) is enabled
Test connectivity with ping
Add static routes or fix routing protocols
Always verify the routing table first.
39
Occurs whenever there is more than one path between the source and destination devices
Switching Loop
40
Switching loops are usually an issue with how STP is configured
41
Formed when an error occurs in the operation of the routing algorithm and creates a circular route amongst a group of network devices
Routing Loop
42
Multiple physical connections between routers provide increased redundancy and fault tolerance
Routing loops are caused by logical Layer 3 circular connections that may exist in a routing table
43
Routing configuration that stops a route from being advertised back in the direction from which it came
Split Horizon
44
Increasing a router's metric to an infinitely high number after detecting one of its connected routes has failed
Route Poisoning
45
Prevents bad routes from being restored and passed to other routers by accident
Hold-Down Timer
46
Selecting and configuring the right protocols properly mitigates routing loop problems
Statically-created routes are given a metric of 1 by default
47
Q: What types of loops are covered in this lesson?
Switching loops (bridging loops)
Routing loops
48
Q: What is a switching loop?
A switching (bridging) loop occurs when more than one path exists between a source and destination at Layer 2.
Multiple paths + no protection = loop risk.
49
Q: Why are switching loops dangerous?
Broadcast packets are flooded out all switch ports and get repeated endlessly, causing a broadcast storm.
50
Q: Why are switching loops common in modern networks?
Modern networks use multiple physical connections for load balancing and fault tolerance, which naturally creates loops.
Redundancy requires loop-prevention mechanisms.
51
Q: How do you prevent switching loops?
Enable Spanning Tree Protocol (STP) on switches.
STP is the primary Layer 2 loop-prevention protocol.
52
Q: How do you verify STP status on a switch?
show spanning tree
53
Q: How does STP prevent switching loops?
STP places some switch ports into a blocking state, allowing only selected ports to forward traffic.
Blocking ports = no Layer 2 loop.
54
Q: What should you do if you suspect a switching loop?
Escalate to a network administrator or network engineer to troubleshoot and reconfigure STP.
Switching loop issues are almost always STP configuration problems.
55
Q: What is a routing loop?
A routing loop occurs when routing algorithm errors create a circular Layer 3 path between routers.
Routing loops are logical, not physical.
56
Q: What causes routing loops?
Incorrect routing protocol configuration
Incorrect routing table entries
Improper static routes
Routing loops happen at Layer 3, not Layer 2.
57
Q: How does TTL prevent routing loops?
Each packet has a Time To Live (TTL) value; when it reaches 0, the router drops the packet, stopping the loop.
58
Q: What is split-horizon and how does it prevent routing loops?
Split-horizon prevents a router from advertising a route back to the router it learned it from.
59
Q: What is route poisoning?
When a route fails, the router sets its metric to an infinitely high value to mark it unusable.
60
Q: What are hold-down timers and why are they important?
Hold-down timers prevent bad routes from being re-advertised.
Used with distance vector protocols like RIP
Default RIP hold-down = 180 seconds (3 minutes)
61
Q: Why are static routes risky?
Static routes have a default metric of 1, making them more trusted than dynamic routes (OSPF, RIP, BGP, EIGRP). Only directly connected routes are trusted more.
Misconfigured static routes are a major cause of routing loops.
62
Network security device that monitors and filters incoming and outgoing network traffic based upon established rule sets
Firewall
63
Runs on an individual computer or device connected to the network to protect that one device
Host-based Firewall
64
Deployed in line with the network traffic flow to monitor and filter incoming and outgoing network traffic based on established rule sets
Network-based Firewall
65
Network connectivity issues experience will be cause by one of three different situations
1. Access to protected resources from unprotected networks is not working
2. Access to unprotected resources from protected networks is not working
3. Access to the firewall and its configurations is not working
66
Either traffic is not going THROUGH or not going TO the firewall properly
67
So when you're writing or editing an ACL rule, always be careful think through what you're inteding to do with that rule
Ensure there are no typos in the rules
Verifty the protocol and port numbers referenced by the rule are correct
Verify the source and destination addresses are referenced by the rule
Verify the order of the rules is applied correctly (ACLs top of the list to the bottom of the list)
68
Between a private internal network and the public internet or between internal networks using screened subnets.
Exam Takeaway:
Firewalls act as an inspection barrier.
69
Q: What are the two main types of firewalls?
Host-based firewalls (software on individual devices)
Network-based firewalls (hardware or virtual devices in-line with traffic)
70
Q: What is a host-based firewall?
A software firewall that protects one individual device, such as Windows Defender Firewall, filtering traffic in both directions.
Host-based firewalls protect endpoints, not entire networks.
71
Q: What is a network-based firewall?
A security device deployed inline near the gateway router that filters traffic for the entire network.
72
Q: What are the three common firewall problem scenarios?
Protected resources not accessible from unprotected networks
Unprotected resources not accessible from protected networks
Inability to access the firewall or its configuration
73
Q: What troubleshooting approach should be used for firewall issues?
Use the seven-step troubleshooting method and troubleshoot using the OSI model from Layer 1 upward.
74
Q: How do you verify Layers 1–3 when troubleshooting a firewall?
Layer 1: Check cabling and link lights
Layer 2: Verify ARP/MAC communication
Layer 3: Verify IP address, subnet mask, and default gateway
75
Q: What is the most common cause of firewall traffic issues?
A misconfigured access control list (ACL).
76
Q: What is an access control list (ACL)?
A collection of permit and deny rules that control which traffic is allowed or blocked.
77
Q: How do you view ACLs on a Cisco network firewall or router?
show access-lists
78
Q: Why can a single ACL rule block all web access?
Denying TCP any-to-any blocks ports 80 (HTTP) and 443 (HTTPS), which websites require.
79
Q: Why can blocking UDP port 123 cause time synchronization issues?
Because NTP uses UDP port 123, and blocking it breaks time synchronization.
80
Q: What are the four critical things to verify when writing ACL rules?
No typos
Correct protocol (TCP vs UDP)
Correct ports
Correct source and destination IPs and subnet masks
81
Q: Why is ACL rule order critical?
ACLs are processed top-down, and the first matching rule wins. Specific rules must come before generic rules.
82
What are the 4 types of IP configurations issues
IP address
subnet mask
default gateway IP
dns sever IP
83
Q: Why is this NOT a standard Class C network?
Because the subnet mask is 255.255.255.128, not 255.255.255.0, meaning it is not a /24 network.
84
Q: What CIDR notation corresponds to the subnet mask 255.255.255.128?
/25
85
Q: How many usable IP addresses are available in a /25 network?
126 usable IP addresses
86
Q: What are the network and broadcast addresses for 192.168.1.0/25?
Network address: 192.168.1.0
Broadcast address: 192.168.1.127
87
Q: What is the usable host IP range for 192.168.1.0/25?
192.168.1.1 – 192.168.1.126
88
Q: Why is the client IP address 192.168.1.200 a problem?
Because 192.168.1.200 is not in the same subnet as the default gateway 192.168.1.1 when using a /25 subnet mask.
89
Q: What subnet does 192.168.1.200 belong to with a /25 mask?
The 192.168.1.128/25 subnet.
90
Q: What are the network and broadcast addresses for 192.168.1.128/25?
Network address: 192.168.1.128
Broadcast address: 192.168.1.255
91
Q: What should you check if websites don’t load by domain name?
92
Q: Why must the IP address and default gateway be in the same subnet?
So the device can route traffic to the gateway.
93
Q: What does the subnet mask 255.255.255.128 represent?
/25 with 126 usable IP addresses
94
Q: What does a /25 do to a Class C network?
Splits it into two subnets.
95
Q: What are the two /25 subnets in 192.168.1.0?
192.168.1.0–127
192.168.1.128–255
96
Q: What public DNS servers should you memorize?
Q: What public DNS servers should you memorize?
97
Q: If IP addresses work but domain names don’t, what should you check?
DNS configuration
98
Q: What must DNS entries point to?
Real, working DNS servers
99
Q: Why do VLANs need routing to communicate?
A: Devices in different VLANs cannot communicate unless traffic is routed through a router.
100
Q: Can devices in the same VLAN communicate without routing?
A: Yes, as long as they are in the same logical subnet.
101
Q: What subnet should all devices in a VLAN share?
A: They should share the same IP subnet (e.g., IT VLAN: 192.168.1.0/24).
102
Q: What is the simplest solution to allow VLAN communication?
A: Connect each switch to a router and assign router interfaces in the corresponding VLAN subnets.
103
Q: What is the main cause of VLAN communication issues?
A: Improper VLAN configuration or lack of routing between VLANs.
104
Q: What happens if VLANs are not used?
A: All devices remain in the default VLAN 1, creating a large broadcast domain.
105
Q: Why is keeping all devices in VLAN 1 a problem?
A: Too many broadcasts slow down the network, especially for servers.
106
Q: How can server performance be improved in a VLAN setup?
A: Place servers in a separate VLAN with other servers to reduce broadcast traffic.
107
Q: Can VLANs span multiple switches?
A: Yes, but proper VLAN tagging and routing must exist for cross-switch communication.
108
Q: What is the function of a router in a VLAN setup?
A: Provides a gateway for each VLAN, allowing inter-VLAN routing and internet access.
109
Matches domain names with the corresponding IP addresses used by a server
DNS
110
Determine if the issue is on a single network client or on a larger network
111
Exam Takeaways (High-Yield)
VLANs segment broadcast domains to improve network performance.
Devices cannot communicate across VLANs without a router or Layer 3 switch.
Each VLAN should have its own subnet.
Proper router interfaces or SVIs are required for inter-VLAN communication.
Avoid putting too many devices in VLAN 1, especially servers.
Segregating servers and clients into separate VLANs reduces broadcast traffic and increases speed.
112
Verify that the A records and the CNAME records were properly created
113
Allows synchronization of system clocks between different layers of a hierarchical, semi-layered system of time sources |Not received, not processed, have errors or packet loss
NTP
114
Ensure proper connection between clients and servers
Verify communication between clients and servers using MAC addresses
Verify communication between clients and servers using IP addresses
Ensure network client is operating the NTP service
115
No network saturation
Adequate network connectivity
116
What is the first step when troubleshooting a DNS problem?
Determine whether the issue affects one client or multiple clients across the network.
117
Q: If only one client has DNS issues, what is the most likely cause?
Incorrect TCP/IP configuration on that client.
118
Q: How do you identify which DNS server a client is using?
Run ipconfig, ifconfig, or ip commands to view the configured DNS server IP.
119
Q: What should you verify after identifying the DNS server IP?
Confirm connectivity between the client and the DNS server.
120
Q: If a client cannot reach its DNS server, what layers should be troubleshot?
OSI Layers 1, 2, and 3 (physical, data link, and network).
121
Q: What should you try if the client can reach the DNS server but DNS still fails?
Flush the DNS cache
Configure a different DNS server (e.g., Google DNS)
122
Q: What public DNS servers can be used for testing or as alternatives?
8.8.8.8
8.8.4.4
123
Q: When should you troubleshoot the DNS server itself?
When multiple clients have issues and client configurations appear correct.
124
Q: What must be verified in DNS A records?
IP address is entered correctly
Domain name is spelled correctly
125
Q: What must be verified in DNS CNAME records?
Both the source and destination domain names are spelled correctly.
126
Q: What command can be used to verify DNS records?
nslookup
127
Q: How can DNS Time To Live (TTL) settings cause problems?
If TTL is too high, old DNS records stay cached too long, delaying updates.
128
Q: What are common causes of NTP issues?
NTP packets not received
NTP packets not processed
Packet loss or excessive delay causing time drift
129
Exam Takeaways (High-Yield)
DNS issues often involve domain names failing while IP access works.
Identify whether the issue is client-specific or network-wide.
Confirm DNS server connectivity before changing settings.
A records map domains to IPs; CNAME records map aliases to domains.
Use nslookup to verify DNS records.
High TTL values can cause stale DNS caching.
Distant DNS servers increase latency.
NTP is critical for authentication and secure communications.
NTP issues commonly result from packet loss, delay, or network congestion.
130
Tracy in the Sales department is experiencing difficulties accessing certain resources and applications critical for their work. Despite having proper network connectivity, they are unable to connect to the sales database and customer relationship management system. The IT department suspects a network configuration issue is causing the problem. Which of the following is the most likely cause of the reported network issues?
Incorrect VLAN assignment - can segregate devices, causing connectivity issues to specific resources
131
In a bustling office environment, employees rely heavily on the company's Wi-Fi network to access resources, collaborate, and communicate. However, lately, users have been encountering difficulties connecting their devices to the network. Despite being within range of the Wi-Fi access points, devices struggle to obtain IP addresses and often fail to connect to the network altogether. The IT department is tasked with resolving these connectivity issues promptly. Which of the following could be the likely cause of the reported network issues?
Address Pool Exhaustion - when all available IP addresses are assigned, preventing new devices from connecting.
132
In a large office building, the IT department recently implemented a new subnetting scheme to accommodate the growing number of devices on the network. However, some employees are reporting issues with connecting to certain network resources. Despite having proper network connectivity, they are unable to access shared folders and printers. The IT team suspects a network configuration issue is causing the problem. Which of the following could be the likely cause of the reported network issues?
Incorrect subnet masks - can lead to devices being unable to communicate properly within the network.
133
In a network environment, users report intermittent connectivity problems and sluggish performance. Upon investigation, it's revealed that multiple switches are interconnected without proper spanning tree protocol (STP) configuration. What is the likely cause of the network issues?
Network Loop - In this scenario, the absence of proper STP configuration allows loops to form in the network, leading to broadcast storms and degraded performance.
134
A user is unable to access webpages on the internet despite being connected to the company's network. You have verified that they are connected to the proper network/SSID. Of the following, which would be the most likely cause of this issue?
Incorrect default gateway - prevent the user from accessing external entworks like webpages o nteh internet.
Network +
flashcards
Decks in class (26)
# Cards
-
Network Fundamentals67
-
OSI Model77
-
Ports and Protocols47
-
Media and Connectors93
-
Distribution Systems39
-
Wireless Networks57
-
Ethernet Switching144
-
IP Addressing128
-
Routing63
-
Network Services51
-
Wide Area Networks (WANs)38
-
Cloud and the Datacenter77
-
Network Security Fundamentals46
-
Network Attacks62
-
Logical Security75
-
Network Segmentation90
-
Network Monitoring95
-
Orchestration and Automation50
-
Documentation and Processes59
-
Disaster Recovery46
-
Troubleshooting Methodology14
-
Troubleshooting Tools92
-
Troubleshooting Physical Networks145
-
Troubleshooting Wireless Issues57
-
Troubleshooting Network Services134
-
Troubleshooting Performance Issues66
